As an anti-glare strategy for cutting reflected light from a water surface, polarizing glasses with polarizing lenses fitted therein has been previously used.
Polarizing performance of the polarizing lens depends on a polarizer. The polarizer is generally a stretched sheet of polyvinyl alcohol having a thickness of 100 μm or less, and the same sheet is dyed with iodine or a dichroic dye to enhance a polarization degree.
However, since the polyvinyl alcohol-based polarizer is a sheet which is weak in physical strength, is poor in hygroscopicity resistance, and is flimsy, it is difficult to make a lens with only the polarizer, and it is said that anti-glare glasses having high practicality are obtained with difficulty.
For this reason, the polarizer is held between resin sheets or glass substrates to physically reinforce it, and an environmental measure of change in humidity is taken to obtain a lens, which is fitted in a glasses frame to obtain polarizing glasses.
A general form of the polarizing glasses is twin-lens type polarizing glasses in which a right eye lens and a left eye lens are independent. The twin-lens type glasses are made by placing separately made polarizing lenses into a twin-lens glasses frame.
To the contrary, single-lens type polarizing glasses have been also made. A laminate structure in which a polarizer is held between resin sheets is called a polarizing plate (See e.g. JP-A No. 1-22538) and, for example, when polycarbonate is used as a resin sheet, it is called polycarbonate polarizing plate.
When this polycarbonate polarizing plate is punched into a single-lens shape, and this is bending-processed into a cylindrical (toric) shape along a facial surface, or a polycarbonate resin is injection-molded as a backup resin on a concave side of the bending-processed polarizing plate, a single-lens type polarizing lens can be made.
When the finished single-lens type polarizing lens is trimming-polished, if necessary, and a nose pad and a glasses frame are mounted, single-lens polarizing glasses can be made (This is present as a commercially available product).